Phase change materials are widely used in various thermal management applications. Conductive nanoparticles can be added to phase change materials to improve their thermal conductivities. The selection of suitable nanoparticles and weight percent is important from thermal performance point of view. In this study, various nanoparticles (e.g. SiO2 (11 nm, 20 nm), Al2O3, Fe2O3, ZnO) and their combinations at different concentrations (2, 4, 6 and 8% wt) were used as thermal conductivity promoters to produce modified paraffin samples. Thermal properties of the synthesized nanocomposites were characterized by differential scanning calorimetric technique. Experimental measurements showed that the presence of nanoparticles can improve thermal conductivity of the nanocomposite (by a maximum of 150%) but the specific heat may be degraded (by a maximum of 39% max). Experimental results have indicated that considering all parameters involved, composite samples with 8 wt% ZnO offer optimum thermal properties. Therefore, it is very important to identify the type and optimum amount of the nanoparticles which are added to the phase change materials. The results of this study can be used to improve thermal performance of nanocomposites phase change materials. (C) 2016 Elsevier Ltd. All rights reserved.